September 3, 2010

Still no evidence of chronic wasting disease in S.C. white-tailed deer

Surveillance conducted by the S.C. Department of Natural Resources over the last eight years continues to provide no evidence of chronic wasting disease in South Carolina.

Like fish and game agencies in most states, the S.C. Department of Natural Resources (DNR) has been diligent in conducting surveillance for the disease in recent years. Sampling has been conducted in all counties and over 4,000 deer have been tested. The sampling methodology used by the department is designed to detect chronic wasting disease (CWD) in the population, even if the prevalence was very low. Surveillance will continue this deer season and DNR's goal is to sample an additional 500 deer stratified at the county level.

Chronic wasting disease is a transmissible spongiform encephalopathy (TSE) that affects deer and elk, according to Charles Ruth, DNR Deer and Wild Turkey Program coordinator. Although the disease has not been diagnosed in South Carolina, it has been found in 18 states and two Canadian provinces. TSEs are fatal neurological diseases characterized by degeneration of the brain. TSEs that affect other animals include scrappie in sheep, bovine spongiform encephalopathy (commonly called "mad cow disease") in cattle, and Creutzfeld-Jakob disease in humans. There is no indication that CWD of deer and elk can be transmitted between species other than cervids (deer family), and both the World Health Organization and federal Centers for Disease Control have indicated that there is currently no indication that the disease can infect humans.

"CWD attacks the central nervous system of the deer or elk and presents symptoms including extreme weight loss, excessive salivation and urination, odd behavior and poor coordination," Ruth said. "The disease in deer or elk is infectious, communicable and always fatal. CWD has a prolonged incubation period (up to five years), and no current test exists to detect the disease in live animals. Diagnosis requires examination of the brain or lymph nodes."

The CWD agent is believed to be a prion, a mutated protein that causes normal proteins in the body to fold abnormally, which causes sponge-like holes in the brain. It is not known exactly how CWD is spread, but it is believed that the agent may be spread both by direct animal-to-animal contact and indirectly by contact with a previously contaminated surface like the soil. CWD has been diagnosed in Colorado, Illinois, Kansas, Michigan, Minnesota, Missouri, Montana, Nebraska, New Mexico, New York, North Dakota, Oklahoma, South Dakota, Utah, Virginia, West Virginia, Wisconsin, Wyoming, and the Canadian provinces of Alberta and Saskatchewan.

South Carolina should continue to have low risk of having a problem with CWD for two reasons, Ruth said. First, South Carolina is geographically far from any known CWD. Second, there is evidence that movements of deer/elk for commercial purposes may have played a role in the current CWD situation, and DNR has historically had a closed-door policy on importation of cervids for commercial purposes like deer farming or ranching.

DNR plans to continue CWD surveillance at some level for the foreseeable future, according to Ruth. "There is simply too much at stake not to make every effort to protect the state's white-tailed deer resource and the deer hunting tradition," Ruth said. "Not only are white-tailed deer the designated state game animal, but the economics associated with deer hunting in South Carolina are very important with more than $200 million in annual retail sales being generated at the local level."